1. Field of the Invention
This invention relates to stage monitors for musical instruments, and more specifically to improvements in such monitors for minimizing feedback problems arising therein by electronic filtering.
2. Prior Art
The use of electronic circuits in conjunction with musical instruments has become well known in the art. Such circuitry is typically used in various synthesizers, where variable filters are provided for achievement of particularly desired special effects. Such a system is disclosed in Whittington et al. U.S. Pat. No. 4,106,384.
Active multiple-stage distributed filters are similarly used in conjunction with electric pianos, organs, and other keyed instrument to attain desired voicing characteristics, tone coloration, and the like. Uetrecht U.S. Pat. No. 4,218,950 illustrates such use, in which undesirable upper harmonics, as well as frequencies below the fundamental are rejected to decrease intermodulation distortion and to increase isolation between the filter stages.
A further use of active filters, having amplifiers connected to capacitive networks, to provide a voltage controlled arrangement for an electronic synthesizer is disclosed in Luce U.S. Pat. No. 3,974,461.
Stage monitors for all, or a selected portion, of a musical program are used to enhance a performer's ability to adjust his own instrument to that of the overall program. For drum systems, however, such monitors introduce significant problems, such as sustained low-frequency feedback. A typical prior art approach to the feedback problem is to stuff a bass drum with pillows, blankets, or drapes, or to provide other forms of mechanical damping therefor.
The use of mechanical devices, however, tends to affect the tonal quality of the music produced by a drum, or other musical instrument, since such music is itself inherently a mechanical vibration.
While prior usage of electronic filtering circuits is known, no such circuits have been devised for minimization of a particular broad band of frequencies contributing to the feedback problem in stage monitors. As is apparent from the above described publications, typical use of electronic circuitry is in enhancement or modification of instrument output, and not in interference with a feedback loop, particularly of the type arising in a stage monitor for a percussive instrument.